1. Field of the Invention
The invention concerns a method and a device for navigation of an endoscopy capsule.
2. Description of the Prior Art
An endoscopy capsule of a general type is known from DE 101 42 253, for example. This conventional endoscopy capsule contains at least one camera that sends up-to-date images or a live video image. Such capsules can include different inspection, diagnosis or therapy devices. For example, this can be a video camera, a biopsy pincer, a clip or a pharmaceutical reservoir. The capsule furthermore contains a magnetizable or permanent magnet element which the capsule is moved wirelessly in the patient. For this purpose. the patient is situated wholly or partially in an electrical coil system composed of multiple (14, for example) individual coils. Suitable magnetic fields or, respectively, gradient magnetic fields are generated by the coil system, which magnetic fields or gradient magnetic fields generate forces or, respectively, torques at the capsule, namely at the magnetic element located in the patient. The capsule in the patient thus can be specifically moved in arbitrary directions. Areas of use are primarily hollow organs, in particular the human gastrointestinal tract (for example) that can be traversed in its entirety with the capsule in a single pass.
The aforementioned complete system or examination method is also called MGCE (magnetically guided capsule endoscopy). In a first generation of these apparatuses or capsules, the respective spatial location of the capsule in the coil system or relative to the coil system is not known, since the system does not possess an expensive and elaborate positioning system. The user, who manually controls the capsule by operating the system, therefore cannot see or locate the capsule extracorporeally.
In principle, such a capsule in the patient could easily be made visible with the aid of x-rays or fluoroscopy, but the x-ray exposure to the patient and the costs for a corresponding system expansion are counter-considerations. Accordingly, the user must orient himself or herself in the patient solely by using the images delivered by the capsule or an additional endoscope introduced into the patient in order to be able to control the capsule in a desired direction or at a desired location in the patient.
Only the current solid angle or the orientation of the longitudinal axis of the capsule in space or the coil system can be set from the outside, thus by the coil system. The desired direction is namely applied by a homogeneous magnetic field. The capsule aligns with its middle longitudinal axis corresponding to this homogeneous magnetic field. However, given a parallel alignment of magnetic moment of the capsule and external magnetic field the force on the capsule due to the corresponding cross-product is zero. It consequently takes a certain period of time until the capsule becomes aligned in this desired direction of the homogeneous magnetic field. Moreover, since the capsule floats in fluid (for example in the stomach), an oscillation of the capsule or a temporal deviation from the desired spatial direction can occur due to sloshing of the fluid, for instance as a result of peristalsis, heartbeat or breathing movements, since the capsule is held in this direction only by small forces.
The control and navigation of an endoscopy capsule in a patient without the aforementioned absolute knowledge of the precise capsule location in the system is thus not achieved in a satisfactory manner in conventional systems.